Field of the Invention
The present invention relates to a wireless power supply apparatus using magnetic resonance that is used in a linear motion type robot.
Description of the Related Art
Conventionally, linear motion type robots (or liner motion type transfer robots) are used in a wide range of facilities, such as factories. A typical linear motion type robots includes a movable unit that moves along a fixed rail unit that is linear or curved in shape. The movable unit has a motor and moves along the rail unit using force generated by the motor. In a conventional linear motion type robot such as this, power is supplied from a power supply to the motor via a power supply cable that is housed in a cable housing member, such as a cableveyor (registered trademark). However, in a linear motion type robot that includes the cable housing member, the movable unit moves, by necessity, so as to pull the cable housing member along with itself. Therefore, the motor that drives the movable unit is required to provide output that takes into consideration the weight of the cable housing member, in addition to the weight of the movable unit and the weight of a member to be carried by the movable unit. As a result, the size of the motor driving the movable unit increases, leading to increased size of the overall robot equipment.
Therefore, supplying power wirelessly between a fixed unit and a movable unit is being considered. As a result of power being supplied wirelessly from the fixed unit to the movable unit, members required for power supply, such as the cable housing member, are eliminated. Therefore, weight reduction and reduced output from the motor can be achieved, leading to size reduction of the overall equipment.
In wireless power supply, a gap is, of course, formed between the fixed unit on the power transmission side and the movable unit on the power reception side. When foreign matter, such as a piece of metal, becomes stuck in the gap, there is concern that an induction current, such as an eddy current, will be generated in the foreign matter, thereby causing heat generation in the foreign matter. Therefore, JP-2012-90373 proposes detecting foreign matter by Q values detected in the power-transmission-side coil and the power-reception-side coil, on the power reception side. In addition, JP-A-2013-17247 proposes directly detecting heat generation in foreign matter using a temperature sensor.
However, in both JP-2012-90373 and JP-A-2013-17247, described above, foreign matter cannot be detected unless the foreign matter becomes stuck between the power-transmission-side coil and the power-reception-side coil. In other words, in JP-2012-90373 and JP-A-2013-17247, variations in the Q value and heat generation in the foreign matter do not occur unless power is transmitted from the power transmission side to the power reception side. Therefore, in the techniques disclosed in JP-2012-90373 and JP-A-2013-17247, there is a problem in that early detection of foreign matter is difficult and safety is low. In a robot which requires reduced size, the gap between the power-transmission-side coil and the power-reception-side coil also becomes small as a matter of course. When foreign matter cannot be detected unless the foreign matter is stuck between the power-transmission-side coil and the power-reception-side coil, if the foreign matter becomes stuck in the gap between the coils that has become smaller in accompaniment with size reduction, jamming may occur and the functions of the robot may be hindered. In addition, in a linear motion type robot that uses wireless power supply, increase in size of the overall robot equipment due to additional apparatuses is not desirable. In other words, JP-A-2013-17247, in which foreign matter is detected based on image information captured by a camera and a temperature sensor is used, is problematic in that additional apparatuses are required and the technique is not suitable for robot equipment.
Therefore, an object of the present invention is to provide a wireless power supply apparatus for a linear motion type robot that detects, with high accuracy and at an early stage, foreign matter that may be stuck between a power transmission coil and a power reception coil, without requiring additional equipment.